DOS ain't dead

Jwasm 2.0 and 64 bit real mode (Announce)

posted by Rugxulo , Usono, 13.10.2009, 02:31

> Hello Japheth and all,
> I see that that jwasm 2.0 production release was posted today on
> http://www.japheth.de/
> I read the "64bit DOS sample" comments on this forum & my question is
> this: What can be done with this mode?
> You call it 64bit real mode, what memory limitations does it have?
> Using the sample code "Dos64.asm" as a model, would it be possible to
> write DOS programs/device drivers/command processors that uses this mode?
> Could a 64bit Real Mode DOS be written that would be backwards compatable
> with 16bit DOS?
> Best regards, Stephen William Foyle

In lieu of Japheth's expert advice while we wait for his reply, I'll give my lame n00b opinion:

64-bit mode is incompatible with 16-bit (which most people consider obsolete). DOSEMU 1.4.0 can run on 64-bit Linux (e.g. XUbuntu 8.04.1 is what I tried), but it has to emulate the 16-bit stuff since there is no V86 mode. In other words, it ain't perfect (some bugs), but it more or less runs pretty well. 32-bit DJGPP stuff is able to run almost natively (albeit with BIOS emulation and DOS API translation too). Of course, that used vanilla FreeDOS 1.0 as the actual DOS (although MS or DR probably work too).

Japheth's example is apparently not using the BIOS or any memory managers or device drivers. In other words, it's pretty raw stuff. Calling it "DOS" is a stretch, it just runs "on top" of DOS at the beginning.

Can you access more than 3-4 GB in DOS? Probably, via PAE (see DOS/32A hack). Is it going to happen? Unlikely. Sure, anything's possible, but a lot of stuff might have to be emulated due to hardware limitations.

Complete thread:

• Jwasm 2.0 and 64 bit real mode - swf, 12.10.2009, 22:49 (Announce)
  • Jwasm 2.0 and 64 bit real mode - Rugxulo, 13.10.2009, 02:31
  • Jwasm 2.0 and 64 bit real mode - Japheth, 13.10.2009, 11:08
    • Jwasm 2.0 and 64 bit real mode - Jack, 13.10.2009, 20:32
    • Jwasm 2.0 and 64 bit real mode - RayeR, 14.10.2009, 00:36
      • Jwasm 2.0 and 64 bit real mode - Japheth, 14.10.2009, 06:08
        • Jwasm 2.0 and 64 bit real mode - RayeR, 14.10.2009, 13:18
          • Jwasm 2.0 and 64 bit real mode - ecm, 14.10.2009, 14:14
            • Jwasm 2.0 and 64 bit real mode - Rugxulo, 19.10.2009, 10:44
      • Jwasm 2.0 and 64 bit real mode - Jack, 14.10.2009, 10:34
        • Jwasm 2.0 and 64 bit real mode - RayeR, 14.10.2009, 13:41
        • Jwasm 2.0 and 64 bit real mode - swf, 14.10.2009, 16:01
          • "Extended" Memory With XMGR. - Jack, 14.10.2009, 19:51
            • "Extended" Memory With XMGR. - swf, 15.10.2009, 18:57
              • "Extended" Memory With XMGR. - Jack, 15.10.2009, 19:42
        • Jwasm 2.0 and 64 bit real mode - Zyzzle, 15.10.2009, 07:35
          • Over 4-GB For UIDE/RDISK. - Jack, 15.10.2009, 09:19